Large communication systems often comprise a plurality of networks which may be connected with each other via a network interconnect solution. Usually, each network of the communication system comprises a plurality of network nodes which are interconnected through internal links, whereas the networks as a whole are interconnected via external links.
In order to ensure a reliable communication between the networks, there have to be rules about which actions should be taken in each network in case of network changes like a network node failure, an internal link failure, or an external link failure.
Service interfaces generally provide different service-related capabilities such as one or more of service selection, priority selection and service access protection. The Provider Backbone Bridged Network (PBBN) standard defines various service interface types. So-called type III service interfaces represent node redundant service interfaces. Type III service interfaces are controlled by the Layer 2 Gateway Protocol (L2GP) and may form the basis of a node redundant network interconnect. The term “node redundant” indicates that the network interconnect is able to “survive” a node failure.
It has, however, been found that a node redundant network interconnect based on type III service interfaces cannot always satisfactorily cope with network changes like a network node failure, an internal link failure, or an external link failure. As an example, a failure in a first network may in certain situations propagate in a second network. Specifically, if an active edge node of the first network has a failure, the active service interface link (i.e., an external link) to the second network may change, so that the second network has to adapt accordingly. Moreover, certain service-related assignments of a first network and a second network such as service to External Network Network Interface assignments may be coupled.